A Small Dose of Mercury

Small Dose of Mercury – 04/13/11

A Small Dose of Mercury

An Introduction To The Health Effects of

Mercury

ENVIRONMENTAL AND OCCUPATIONAL TOXICOLOGY III

(ENVH 516)

A Small Dose of Toxicology Small Dose of Mercury – 04/13/11

Mercury the Metal


Key Words

Risk =

Hazard X Exposure

Dose / Response

Individual Sensitivity


What Is This?

Hg

CH3


Methyl Mercury (MeHg)

Hg

CH3


Hg - Inorganic & Organic

Hg

CH3

Inorganic – Quick Silver

Hg

Organic – Methyl Mercury


Hg Facts & Uses

• Quicksilver• 13.6 times the weight of water• Evaporates at room temperature• Bacteria change to Methylmercury• Amalgam• Many Industrial uses

(thermometers, chemical reactions, gold mining)


Hg – Like Water


Hg – Solid Enough to Sit On


• Alchemy• Medicine - cure syphilis?• Egyptian tomb -1500 BC

Ancient Awareness


Greek God Mercury

“For then she bare a son, of many shifts, blandly cunning, a robber, a cattle driver, a bringer of dreams, a

watcher by night, a thief at the gates, one who was soon to show forth

wonderful deeds among the deathless gods...”

Description of the birth of the Greek God Mercury


Occupational ExposureGold mining.

Hatters in the felt industry.

Historical Events


Historical Awareness

A Small Dose of Toxicology Small Dose of Mercury – 04/13/11Polluting with HG

Discharge in Minamata Bay


Fetal Effects of MeHg


Life-Long Effects of MeHg


Planting Seed with Mercury


Iraq Mothers with Bread


Iraq Infant - Effects of Mercury


Coal Fired Plants – Hg Emissions


Outbreaks of MeHg Poisoning

Place Year CasesMinamata 1953-60 1000

Nigata 1964-65 646

Guatemala 1963-65 45

Ghana 1967 144

Pakistan 1969 100

Iraq 1956 100

Iraq 1960 1,002

Iraq 1971 40,000

On-going 2001 ???


Inorganic - elemental mercury vapor Hg0

Inorganic - elemental mercury vapor Hg0

Biotransformation

Organic - Methylmercury - CH3Hg+

Bioaccumulation

Mercury to Methyl Mercury


Mercury Release

50-75% mercury of released in the environment related to human activities


Atmospheric Hg


Ambient WaterSediments

Edible Fish

Inorganic Mercury

Methyl-Mercury

Methyl-MercuryIn Humans

Biomethylation

Bioaccumulation

Exposure

Discharge

Biotransformation of Mercury


• Natural Degassing of the earth• Combustion of fossil fuel• Industrial Discharges and Wastes• Incineration & Crematories• Dental amalgams

Hg0 Hg2+ CH3Hg+

Environmental Sources of Mercury


The Mercury Cycle


A 270-year record

Major atmospheric releases•Natural

•Background (42%)•Volcanic (6%)

•Anthropogenic (52%)•Gold rush•WWII•Industrialization

Significantly The last 100 years

anthropogenic: 70%

The last 10 yearsan apparent decline


• Blindness - Deafness• Cerebral Palsy - Seizures• Abnormal reflexes & muscle tone• Retarded motor development• Visual and Auditory Deficits• Delayed motor development• Altered DRH performance

Neurobehavioral Effects


• Decrease in Brain Size• Cell loss• Disorganization of cells• Cell migration failures

Effects On The Brain


MONKEY - 25 µg/kg - LOAELRAT - 10 µg/kg - LOAELRAT - 50 µg/kg - replicated

Animal - Risk Assessment


2.5 µg/kg - NOAEL (animals) 0.25 µg/kg - Human 0.025 µg/kg - Sensitive populations

Animal - Risk Assessment

(the rule of dividing by 10)


• 10-20 ppm hair - LOAEL •• 40-80 ppb blood - LOAEL •

• 0.645 µg/kg •• 0.06 µg/kg - RfD •

Human - Risk Assessment


Mercury Fishing Advisories

49 States have over 2000 fish consumption advisories

An increase from 27 in 1993 Pregnant women, nursing

mothers, women who intend to have children, and children under 15


• Reduce environmental release

• Restrict global production and sale

• Advise women of child bearing age

• Research mechanisms of action

• Assess neurodegenerative effects

Recommendations


MeHg Consumption Limits

• 1969 - FDA 0.5 ppm action level for total Hg in fish• 1979 - FDA 1.0 ppm raised the action level for total Hg• 1984 - FDA 1.0 ppm switched to MeHg in fish • 1999 - US ATSDR – 0.3 µg/kg-day MRL• 2001 - EPA 0.1 ug/kg oral RfD for MeHg• Later - EPA 0.3 ppm advised MeHg fish tissue level for

human health based upon water quality standards• 2001? - Maine 0.2 ppm action level MeHg (RfD 0.1

ug/kg)• Florida - 0.5 ppm Hg for retail fish and seafood• Canada and EU - 0.5 ppm Hg for retail fish and seafood


MeHg Consumption Limits

• US EPA – 0.1 µg/kg-day RfD

• US FDA – 1 ppm (mg/kg) in fish

• US ATSDR – 0.3 µg/kg-day MRL

• Canada - 0.5 ppm Hg for retail fish and seafood


FDA Fish Consumption Advise

1. Do not eat – as they contain high levels of mercury

Shark Swordfish King Mackerel Tilefish

2. Eat up to 12 ounces (2 average meals) a week of a variety of fish and shellfish that are lower in mercury.

3. Check local advisories about the safety of fish caught by family and friends in your local lakes, rivers, and coastal areas.

(ref - http://www.fda.gov/Food/ResourcesForYou/Consumers/ucm110591.htm)


Mercury A Global Issue

Mercury distribution and exposure is a global problem


Concluding Questions

• Is the FDA action level of 1.0 ppm mercury in fish consistency with our scientific understanding of the health effects of mercury and protective of human health?

• Should the FDA lower the mercury action level to 0.3 ppm?

• Are specific adult consumption advisories needed?

• Should Point of Purchase warnings be expanded?

• Is better consumer advice needed?


Alice’s Adventures

“Everything’s got a moral, if you can only find it”

Lewis Carroll in Alice’s Adventures in Wonderland


A Small Dose of ™ Mercury


Additional Information

Web Sites Toxipedia – Mercury -

http://www.toxipedia.org/display/toxipedia/Mercury

United Nations Environment Program's Global Mercury Assessment. http://www.chem.unep.ch/mercury/

US EPA - Main site on Mercury. http://www.epa.gov/mercury/

The Mercury Policy Project (MPP). - works to raise awareness about the threat of mercury contamination - http://www.mercurypolicy.org/

ATSDR – Mercury - http://www.atsdr.cdc.gov/substances/toxsubstance.asp?toxid=24


Authorship Information

For Additional Information ContactSteven G. Gilbert, PhD, DABT

E-mail: [email protected]: www.asmalldoseof.org

This presentation is supplement to “A Small Dose of Toxicology”


State - Risk Assessment

• 26 States - Fish Advisories• Pregnant women, nursing mothers,

women who intend to have children, and children under 15


• 34 States - Fish Advisories •• 26 of 34 - Women and kids •

• >0.16 ppm limit consumption •

State - Risk Assessment

Documents

A Small Dose of Mercury